Abstract

With the increasing power and sophistication of experimental
and theoretical methods for assigning chemical structures, it seems almost incredible that the structure of any reasonably stable organic entity with a small number of carbons could remain enigmatic for very long. Nonetheless, this is true of C_4H_7^+-one of the first "nonclassical" cations to be discovered, which has some of the characteristics expected for a very rapidly equilibrating
mixture of classical cyclopropylmethyl, cyclobutyl, and 3-butenyl cations and yet other characteristics which wholly belie any description that implies conventional charge distributions or geometries derived from structural representations using solid lines representing
two-electron bonds.